Dental composites placement techniques for direct restorations

ABSTRACT

Colorless dental compositions for restoring the enamel layer of a tooth are disclosed. The colorless enamel compositions are combined with pigmented dentin compositions to provide a true color match and natural esthetics. Methods that utilize the compositions in placement/build-up techniques in direct restorations are also disclosed.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/531,886, filed Dec. 22, 2003.

FIELD OF THE INVENTION

This invention relates to dental composites and methods for their use inplacement/build-up techniques in direct restorations.

BACKGROUND OF THE INVENTION

Dental restoratives are well known in the art and include for example,crowns, inlays, onlays, veneers, and fillings. Restorative materials arethose utilized in repairing a damaged tooth, or in replacing an entiretooth. When repairing a damaged tooth, it is desirable not only that thetooth be returned to a useful state, but that it also be returned asclose as possible to its natural aesthetic state, such that the colorand appearance of the restored tooth blend in with the surroundingnatural dentition.

Dental restorations are typically prepared according to two differenttechniques: (1) in situ or direct restorations, wherein the restorationis fabricated directly in the patient's mouth; and (2) indirectrestorations, wherein the restoration is fabricated directly in a dentallaboratory and subsequently communicated to the dental practitioner forplacement in the patient's mouth. Direct restorations typically involveissues such as repairing a cracked tooth, treating a tooth for decay orfilling in a space between adjoining teeth. Indirect restorationtechniques are typically employed for more complex dental repairs, suchas, for example, the replacement of a complete tooth. Indirectrestorations are typically fabricated from ceramics or porcelains andinvolve the build-up of sequential layers of material. While indirecttechniques are inherently more expensive, time consuming and require agreater level of technical expertise than direct placement techniques,they allow for a higher degree of aesthetic precision and typicallyprovide a very natural looking restoration.

In a typical direct restoration, the tooth to be restored is initiallytreated by removing the decayed or damaged material and then the removedportion is restored with a dental restorative material. Conventionalrestorative materials include dental amalgams or metal alloys; flowabledental composites, such as those described in U.S. Pat. Nos. 3,066,112;3,179,623; and 4,744,759 to Bowen; and condensable dental composites,such as those described in U.S. Pat. Nos. 4,381,918 and 4,392,828 toEhrnford; U.S. Pat. No. 4,952,530 to Brosnan et al.; U.S. Pat. No.5,621,035 to Lyles et al.; and U.S. Pat. No. 6,013,694 to Jia et al.U.S. Pat. No. 6,300,390 to Angeletakis describes resin-based dentalrestoratives incorporating uniformly dispersed submicron sizedreinforcing particulates and published U.S. Patent Application No.2003/0175660 to Yin et al., describes a restorative composite includinga spherical or sub-micron size filler bound together by a polyurethanedimethacrylate ester oligomer.

Dental restorative composites are typically dispersions of micro sizedglass filler particles in a methacrylate-type monomer resin. Splintered,pre-polymerized particles or ground suspensions of silica inpre-polymerized dental resins, may also be used. Additives such aspigments, initiators and stabilizers may be included in these types ofcomposites. Flowable dental composites are typically a reinforcingparticulate inorganic filler bound together by a polymeric matrix. Onecommonly used flowable dental composite is a mixture of an organicpolymer known as bisphenol-A-glycidyl methacrylate (Bis-GMA) andinorganic particles such as quartz, borosilicate glass, and lithiumaluminum silicate. Typical condensable dental composites include variousother alternative inorganic filler materials in a polymer matrix.

Due to their metallic appearance and low adherence to natural toothstructure, the growth of amalgams in dental restorations has remainedflat with increasing growth in current dental practices typicallyutilizing various light-curable dental composites for fabricatingrestorations. In addition to being durable and wear resistant, dentalcomposites are readily adaptable to coloring and can therefore provide amore natural looking restoration.

Conventional composite placement techniques for direct restorationstypically include the steps of:

-   -   cleaning the tooth and while moistened, evaluating the overall        shade/color appearance;    -   preparing the area for restoration, i.e., removing        decayed/damaged enamel and dentin;    -   applying a bonding agent to the prepared area;    -   selecting correspondingly-colored dentin and enamel restorative        materials, respectively;    -   applying the colored dentin material to restore the dentin        layer;    -   applying the colored enamel material to restore the enamel        layer; and    -   finishing and polishing the restoration.

Optional steps might include applying a flowable composite prior toapplying the colored dentin material, in order to fill in any voids orirregularities that may exist in the floor of the restoration area, orapplying special effects to the restoration prior to finishing andpolishing.

One of the most exacting and time consuming aspects of dentalrestorations, whether involving direct or indirect placement techniques,is that of properly matching the color of the restoration to that of theoriginal tooth. In the context of clinical dentistry, the term “color”involves three discrete concepts: hue, chroma and value. Hue is thedimension of color that enables us to distinguish one family of colorfrom another; chroma defines the relative intensity of a particularcolor, i.e., the more intense a color is, the higher its chroma level;and value describes the relative whiteness or blackness of a particularcolor, i.e., the brighter the color, the higher its value. In additionto these concepts, characteristics such as opacity, fluorescence, andtranslucency may also be considered during a dental restoration.

To aid in the determination of tooth color, a dental practitioner willoften utilize a dental shade guide or other such similar device, toevaluate the color characteristics of the tooth. A typical dental shadeguide has a base supporting a plurality of tabs or other indicia, eachof which corresponds to a different color. A given guide may include anumber of sets of tabs, one representing standard tooth colors, onerepresenting standard dentin colors and one representing standard enamelcolors. The colors are typically defined according to the CIE L*a*b*system wherein “L” refers to value (black is 0 and white is 100), “a” isa measurement on the red to green scale, and “b” is a measurement on theblue to yellow scale (Bilmeyer, F. W., Principles of Color Technology,2^(nd) ed., John Wiley, 1981).

Conventional shade guides are disclosed, for example, in U.S. Pat. No.6,315,554 to Coste et al. and U.S. Pat. No. 6,030,209 to Panzera et al.and published U.S. Patent Application Nos. 2003/0124481 to Zun;2002/0081547 to Kerschbaumer et al.; and 2002/0064750 to Morris et al.Commercially available shade guides include Vitapan Classical™(formerly, Vita-Lumin™ Vacuum Shade Guide), Vitapan 3-D Master™ (Vident,Brea, Calif.), Bioform™ and TruMatch™ (Dentsply International, Inc.,Milford, Del.)

Conventional restoration techniques utilize a philosophy that both thedentin and enamel layers of teeth possess a color or shade whichinfluences the overall color and appearance of the tooth. Standard shadeguides categorize these colors into four basic groups: A, B, C, and D.In addition, each group may itself be internally categorized to includeshades that add further characterization to restorations. Darker shades,for example, have been developed for older patients and bleach shadeshave been introduced in response to an increased use of whiteningagents. In practice, the practitioner first chooses the color tab thatmost closely matches the overall color of the damaged tooth. Thecorrespondingly-colored dentin and enamel restorative materials are thenprepared and placed on the tooth. Thus, the color of the finishedrestoration will result from a combination of the colors of the dentinand the enamel restorative materials.

One drawback of this technique is therefore, the high level of skill andeffort required to assure that the colored dentin and enamel materials,when combined, create the appropriate color result so that therestoration blends in with the surrounding dentition. As a result,although conventional tooth-colored composite placement techniquesprovide restorations that are much more aesthetically appealing than hadpreviously been achieved with amalgams, for example, improved techniquescontinue to be sought. Direct placement techniques that provide arestoration having the aesthetic properties of an indirect ceramicrestoration would be highly desirable. The principles of the presentinvention provide such techniques.

SUMMARY OF THE INVENTION

In accordance with the principals of the present invention, a directrestoration having the aesthetic qualities of an indirectly fabricatedceramic restoration is provided. In one embodiment, a method is providedfor fabricating a direct dental restoration having the color of anatural tooth, including:

-   -   matching the value shade of the tooth to be restored to a        colorless enamel value restorative material;    -   preparing the tooth for restoration;    -   matching the shade of a dentin layer of the tooth to a shaded        dentin restorative material;    -   applying the matched dentin restorative material to the tooth to        be restored; and    -   applying, over the dentin restorative material, the matched        colorless enamel value restorative material to the tooth to be        restored.

In a further embodiment there is provided a method for fabricating adirect dental restoration having the color of a natural tooth,including:

-   -   cleaning the tooth and while moistened, matching the value shade        of the tooth to be restored to a colorless enamel value        restorative material;    -   preparing the tooth for restoration by removing decayed/damaged        enamel and dentin or reshaping the tooth for cosmetic        restoration;    -   matching the shade of a dentin layer of the tooth to a shaded        dentin restorative material;    -   applying a bonding agent to the prepared area;    -   applying a flowable composite prior to applying the colored        dentin material, in order to fill in any voids or irregularities        that may exist in the floor of the restoration area;    -   applying the matched dentin restorative material to the tooth to        be restored;    -   applying, over the dentin restorative material, the matched        colorless enamel value restorative material to the tooth to be        restored;    -   applying special effects, including internal characterization        materials including white or blue shaded or staining or tinting        materials to the restoration prior to the final restorative        layer;    -   applying an external characterization material including a        translucent material to the external surface of the restoration;    -   finishing by shaping or contouring the restoration; and    -   polishing the restoration.

In a further embodiment there is provided an enamel restorative materialcolorless to the naked eye, having no added pigment and a low valueshade; a medium value shade; or a high value shade.

In another embodiment there is provided a cured dental compositerestoration including a highly chromatic shaded dentin restorativematerial and an enamel restorative material colorless to the naked eye,having no added pigment and a low value shade; a medium value shade; ora high value shade.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 15 illustrate the clinical case study described inExample 2.

DETAILED DESCRIPTION OF THE INVENTION

The direct restoration technique of the present invention utilizes therecognition that tooth enamel is a colorless material and that the“color” of a tooth resides in the dentin layer. It is the degree towhich the color of the highly chromatic dentin material shines throughthe colorless enamel that determines a tooth's color. In light of thisrecognition, conventional direct restoration techniques which require acolor determination for both the dentin and enamel layers can besimplified in providing natural-appearing and aesthetic restorations.

The present invention utilizes the concept that the color of a naturaltooth is determined by the color of the dentin layer and that the enamellayer is colorless, yet having a value shade. Value shade is theparameter of color that describes its relative brightness or darkness,the higher the value, the brighter the color. The present inventioneliminates the need to select colored restorative dentin materials andcolored restorative enamel materials that when combined match theultimate color of the final restoration. Rather, the practitioner issimply required to match the color of the dentin layer. The tooth isevaluated simply on its value, or level of brightness. The color of therestoration is therefore determined by the “color” of the chromaticdentin restorative material and the value of the “colorless” enamelrestorative material. The enamel restorative material is therefore alsoappropriately referred to as the “value restorative”. In accordance withthe enamel restorative material of the present invention, “colorless”means that the material is colorless to the naked eye. Moreover, nopigment is added to the formulation of the enamel restorative material.

In accordance with the principles of the invention, a new enamel shadegroup referred to as value shades is provided. The group includescolorless shades measured on a scale of black to white. The value shadescontain no hue or chroma dimension that is detectible by the naked eye.Preferably, the group includes three shades, referenced as low value,medium value, and high value. The low value shade is the darkest (i.e.,most closely approaching black), the high value shade is the brightest(i.e., most closely approaching white), and the medium value shade isgenerally in between, however, other groupings are possible. As thevalue shades contain no added pigment, they are inherently moretranslucent than conventional standard enamel shades.

The colorless enamel value shade restorative material typically includesa filler component, a polymer matrix/monomer component, and apolymerization catalyst, such as those known in the art. Suitable fillermaterials include, for example, finely divided solids such as silica,glass, zirconium, aluminum oxide, crystalline quartz, glass beads, ormixtures of glass beads and quartz. The polymeric matrix may be, forexample, an acrylic or epoxy resin or other type of carbon-basedpolymer. Examples of polymeric materials (resins) suitable for use asdental composites are described in U.S. Pat. Nos. 3,066,112; 3,179,623;4,744,759; and 5,997,302, the entire contents of which are incorporatedherein by reference in their entirety.

Thus, in accordance with the method of the present invention, the dentalpractitioner is required to make a “color” match with respect to onlythe dentin layer of the tooth to be restored. The enamel layer isevaluated simply on the concept of value. As conventional directplacement techniques do not consider the concept of value alone, thepresent invention provides a more simplified method for fabricating adirect restoration with a natural looking and aesthetic result.

In accordance with the methods of the present invention, the area of thetooth to be restored is cleaned. Preferably, while the tooth is moistand hydrated, the tooth is evaluated with respect to its value shade,for example, it is matched to a value shade having low value, mediumvalue, or high value. Preferably, the value shade is determined throughthe use of a shade guide that includes the colorless value shadeindicia. The value shade guide may, for example, be adapted to includethree value shade tabs, referenced as low value, medium value, and highvalue, wherein the closest match to the value shade of the tooth isdetermined by comparison with each of the three tabs.

The tooth is then prepped according to conventional preparationtechniques to remove the decayed/damaged portions of the enamel anddentin. Methods for tooth preparation are well-known in the art andinclude for example, acid etching, cavo surface beveling, carbidefriction-grip burs, “blasting” with an air abrasion unit, and“vaporization” with a dental laser. The tooth is then washed with water.While excess water is removed by blotting or by treating with a streamof air, the tooth surface is preferably left moist, as a dry surface canresult in a poor bond between the tooth and the restorative materials.Tooth preparation may also include reshaping of the tooth for cosmeticrestoration with or without removing damaged portions.

Following tooth preparation, the practitioner determines the color ofthe chromatic dentin layer of the tooth. This may be accomplished, forexample, by matching with the aid of a conventional dentin shade guideor other similar procedure. The dentin is matched to a dental compositematerial for use in restoring the dentin layer which has been preparedand colored to correspond to the natural dentin, all according toconventional preparation and coloring techniques.

Following selection of the dentin shade, a thin layer of a bondingagent, such as a primer, an adhesive, or a primer/adhesive mixture, istypically applied. The bonding agent enhances the attachment of therestorative materials to the natural dentin and enamel. Such productsand methods for their application are well-known in the art. Preferably,the bonding agent is applied in two consecutive coats, which are thentreated with air to remove the solvent and cured, typically by exposureto a visible light source for about 10 seconds.

As in conventional direct restoration procedures, a thin (0.5 to 1.0 mm)layer of a flowable dental composite material may optionally be placedin the cavity and cured. This material is commonly used to ensure thatall surfaces and voids within the cavity are wetted, in order to providethe best possible attachment surface for the restorative materials.Materials for use in this step, and methods for their placement, arewell-known in the art. One such method is described in U.S. Pat. No.6,315,567 to Hasel, the entire content of which is incorporated hereinby reference.

The practitioner then utilizes techniques in accordance with the presentinvention to build-up the restoration by placing sequential layers ofrestorative materials within the area to be restored. The dentin-coloredrestorative material is used to restore the dentin layer and optionallya portion of the enamel layer and the colorless enamel-value shaderestorative material is used to restore the enamel layer. Preferably,each of these restorative materials are place in increments of 2 mm andthen polymerized or hardened. Polymerization is typically achieved withthe use of a curing light, although other conventional methods may alsobe used. The restoration is completed with known polishing and finishingtechniques.

Optional steps may include for example, the application of specialeffects shades, such as tinting or staining materials, just below thefinal restorative layer. Special effects may include, for example, awhite or blue shade applied prior to the final colorless enamel-valueshade restorative material, in the case where the natural tooth hadpreviously undergone whitening. These special effects provide internalcharacterization. Frequently, practitioners will also apply a layer of avery translucent material to the external surface of the restoration togive a life-like aesthetic appearance. Typically, such translucentmaterials are categorized as amber, clear or super clear which providesurface or external characterization with translucency levels up to 50%or more.

EXAMPLES Example 1

Below is a listing of the CIELAB color co-ordinates (L*, a*, b*) as wellas the degrees of opacity (CR) and translucency (T) of the high, medium,and low value shade enamel restoration materials of the presentinvention: L* a* b* CR (%) T (%) Value High 76 −1.85 7.3 45 20.0 ValueMedium 73 −1.57 5.5 52 17.3 Value Low 63 −0.6 5.8 47 23.2

Example 2

A 27-year-old female presented with the complaint that she did not likethe spaces between her teeth (FIG. 1). Facially, the diastemas were notas apparent, but she was very aware of the spaces and wanted the problemcorrected. She felt the appearance of her smile would improve if thediastemas were closed.

A clinical evaluation was completed and 35-mm photographs were taken.Diastemas between tooth Nos. 5 and 6, 6 and 7, and 10 and 11 were noted(FIGS. 2 and 3). She demonstrated no pathology and had good occlusalfunction. The patient was not dissatisfied with the color or the overallshape and contour of her dentition.

During the consultation, treatment options were reviewed and thedecision was made to correct the diastemas using a direct compositionsystem (4 Seasons® Direct Esthetic Composite System; Ivoclar Vivadent,Inc., Schaan, LI). A conservative approach was warranted, given thehealth of the surrounding dentition and the patient's overallsatisfaction with the existing color and shape of her teeth. Therefore,the factors to be considered in this case included the following:ensuring that the restorations would match the surrounding dentition;achieving width-to-length ratios that would be acceptable to thepatient; and achieving proper occlusal function. At the time ofpresentation, the width-to-length ratio was 56% to 70%; the ideal wouldbe 80%.

The patient would benefit from a direct veneering technique for severalreasons. Specifically, there would be only one appointment necessary tocomplete the restorations, there would be no temporization, and theresult not only would be noninvasive but also reversible. The directveneering technique would allow the dentist to utilize artistic skillsto create additional tooth structure with the same qualities as thenatural dentition.

The composite system of choice (4 Seasons® Direct Esthetic CompositeSystem) was selected based on the number and accuracy of shadesavailable. The material's “true color confidence” resulted from fouryears of clinical research and testing that produced a true match tostandard A-D shades in addition to mimicking the transparency, opacity,fluorescence, and value of natural tooth structure. With forty compositeshades and shade effects available, it would be possible in this case tomatch even the most aesthetically challenging aspects of this patient'sdentition.

A shade guide (4 Seasons® Shade Guide; Ivoclar Vivadent, Inc., Schaan,LI) was used to determine which shade(s) of composite to place. Theadvantage of using this shade guide is that the shade tabs are made withceramic to ensure long-term color stability and enable a consistentshade match. Once the shades were determined, the selected compositeshades were placed on the unetched tooth surfaces of the mesial aspectof tooth No. 5, the mesial and distal aspects of tooth Nos. 6 and 10,and the distal aspect of tooth No. 7, then light-cured to simulate thepermanent restorations (FIG. 4). This “mock-up” verified accurate shadeselection and provided a basis for the creation of a putty matrix(Virtual Putty™; Ivoclar Vivadent, Inc., Schaan, LI), which would serveas a guide for proper lingual contouring and assist in determining theappropriate length of the permanent restorations (FIGS. 5 and 6).

Once the putty matrix was complete, the interim composite material wasremoved with an explorer or curette and the teeth were then cleansedwith pumice and isolated with cotton rolls. The teeth were acid-etchedwith 37% phosphoric acid for 30 seconds (FIG. 7), rinsed thoroughly, anddried. A light-cured, single-component bonding agent (Excite®; IvoclarVivadent, Inc., Schaan, LI) was applied to the etched surfaces andlight-cured for 10 to 20 seconds (FIG. 8). Once a homogeneous gloss wasapparent on all prepared areas, the surfaces were then ready forplacement of the permanent restorations.

The restorations were placed according to an anatomical technique thatinvolved the use of a highly chromatic dentin shade composite overlaidwith a colorless enamel value composite. In addition to a fullcomplement of enamel and dentin shades that correspond to the A-D shaderange, the selected composite system also featured three unique valueshades (high, medium, and low) that mimic natural enamel in the mannerin which it diffuses the underlying dentin color to create anatural-looking depth and appearance.

The lateral incisors were evaluated, and a dentin shade of A2 wasselected. A thin coating of A2 dentin composite was placed on distalaspects of the lateral teeth, contoured with a brush and compositeinstrument (FIG. 9), then light-cured for 10 seconds with a turbo tip onan Astralis® 10 (Ivoclar Vivadent, Inc., Schaan, LI). The dentin shadewas then overlaid with a medium-value shaded enamel composite, which wasalso light-cured for 20 seconds with a turbo tip on an Astralis® 10since this was the final cure. An A3 dentin composite was then similarlyplaced on the mesial aspects of the canines and cured, after which itwas overlaid with a medium-value shaded enamel composite andlight-cured.

The restorations were shaped and contoured using medium, fine, andsuperfine discs (3M™ ESPE™ Sof-Lex™ Xt; 3M ESPE AG, Seefeld, Germany)(FIG. 10), and the final contours were made with a finishing bur (Axis™TDF9 Finishing Bur, Axis Dental, Irving, Tex.) (FIG. 11). To achieve anice, polished surface a PoGo™ Wheel (DENTSPLY Caulk, DENTSPLYInternational, Inc., York Pa.) and Astropol® points (Ivoclar Vivadent,Inc., Schaan, LI) were used (FIG. 12). The final restorations werephotographed at completion (FIGS. 13 and 14) and again 5 dayspostoperatively (FIG. 15).

Although preferred embodiments have been depicted and described indetail herein, it will be apparent to those skilled in the relevant artthat various modifications, additions, substitutions, and the like canbe made without departing from the spirit of the invention and these aretherefore considered to be within the scope of the invention as definedin the claims which follow.

1. A method for fabricating a direct dental restoration having the colorof a natural tooth, comprising: matching the value shade of a naturaltooth to be restored to a colorless enamel value restorative material;preparing the tooth for restoration; matching the shade of a dentinlayer of the tooth to a shaded dentin restorative material; applying thematched dentin restorative material to the tooth to be restored; andapplying, over the dentin restorative material, the matched colorlessenamel value restorative material to the tooth to be restored.
 2. Themethod of claim 1, wherein applying comprises placing a thin coating ofrestorative material on the object to be applied and polymerizing therestorative material.
 3. The method of claim 2, wherein the restorativematerial is polymerized by light-curing.
 4. The method of claim 1,wherein preparing the tooth for restoration comprises removing a portionof the enamel layer and a portion of a dentin layer of the tooth.
 5. Themethod of claim 1, wherein preparing the tooth for restoration comprisesreshaping the tooth for a cosmetic restoration.
 6. The method of claim1, further comprising applying a bonding agent to the exposed dentin andenamel when preparing the tooth for restoration to enhance the bondingof the composite restorative material.
 7. The method of claim 1, furthercomprising finishing and polishing the restored tooth.
 8. The method ofclaim 7, wherein finishing comprises at least one of shaping andcontouring the restoration.
 9. The method of claim 1, wherein the valueshade of the colorless enamel value material is a low, medium, or highvalue.
 10. The method of claim 1, wherein the colorless enamel valuerestorative material includes a polymerizable resin, filler, andcatalyst.
 11. The method of claim 1, wherein the dentin restorativematerial includes a polymerizable resin, filler, and catalyst.
 12. Amethod for fabricating a direct dental restoration having the color of anatural tooth, comprising: cleaning the tooth and matching the valueshade of the tooth to be restored to a colorless enamel valuerestorative material; preparing the tooth for restoration by at leastone of removing decayed/damaged enamel and dentin and reshaping thetooth for cosmetic restoration; matching the shade of a dentin layer ofthe tooth to a shaded dentin restorative material; applying a bondingagent to the prepared area; applying a flowable composite prior toapplying the colored dentin material, in order to fill in any voids orirregularities that may exist in the floor of the restoration area;applying the matched dentin restorative material to the tooth to berestored; applying, over the dentin restorative material, the matchedcolorless enamel value restorative material to the tooth to be restored;applying special effects, including staining or tinting materials orwhite or blue shade to the restoration prior to the final restorativelayer; applying a translucent material to the external surface of therestoration; finishing by shaping or contouring the restoration; andpolishing the restoration.
 13. A colorless enamel restorative materialhaving no added pigment and a low value shade; a medium value shade; ora high value shade.
 14. The product of claim 13, wherein the low valueshade has a CIELAB co-ordinate of
 63. 15. The product of claim 13,wherein the medium value shade has a CIELAB co-ordinate of
 73. 16. Theproduct of claim 13, wherein the high value shade has a CIELABco-ordinate of
 76. 17. A cured dental composite restoration comprising:a highly chromatic shaded dentin restorative material and a colorlessenamel restorative material having no added pigment and a low valueshade; a medium value shade; or a high value shade.
 18. The product ofclaim 17, wherein the low value shade has a CIELAB co-ordinate of 63.19. The product of claim 17, wherein the medium value shade has a CIELABco-ordinate of
 73. 20. The product of claim 17, wherein the high valueshade has a CIELAB co-ordinate of 76.